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3.3 Special Terms in RFEM
This chapter explains some important terms specific to RFEM. They are described in detail in the following chapters.
In the 3D model, a node is defined by its coordinates (X/Y/Z). Nodes are used to model the geometry of a structure.
Nodes are connected by lines. In addition to straight connections, high-grade lines such as arcs or splines are possible.
A member represents the property of a line.
Through material and cross-section properties, a certain stiffness is assigned to the member.
Set of members
Members can be combined into a set of members.
A surface is limited by lines.
Through material and thickness properties, a certain stiffness is assigned to the surface.
A solid is surrounded by boundary surfaces (usually type Null).
The stiffness is defined by its material properties.
The degrees of freedom are limited for the node.
The degrees of freedom of all FE nodes on a line are limited.
The degrees of freedom of all FE nodes in a surface are limited.
Force or moment applied to a node.
A line is loaded by a uniform or variable distributed load or by a concentrated load. The load acts as a force or moment.
A member is loaded by a distributed or concentrated load. The load diagram can be either uniform, linearly variable, or parabolic. In addition to forces and moments, temperature actions and prestresses are possible.
A surface is loaded by a uniform or linearly variable load. In addition to forces, temperature loads and imposed deformations can act on the surface.
A solid is loaded by effects of temperature or imposed deformations.
The loads from an action are managed in a load case, for example "self-weight" or "wind". The loads should be defined as characteristic loads (i.e. without factors). Partial safety factors can be considered in load or result combinations. A load case is usually calculated according to the linear static analysis.
A load combination is used to superimpose load cases, that means all loads of the load cases in question are summarized. A load combination is usually calculated according to the second-order or large deformation analysis.
A result combination sums up the results of the contained load cases. It is also possible to determine the extreme internal forces and deformations from different load cases, load combinations, or result combinations using an Or combination. However, the additive principle of superposition does not apply for results calculated according to the second-order analysis.